1. Field of the Invention
This invention relates to a substrate treatment device to be used for a semiconductor production apparatus.
2. Description of the Related Art
A reaction furnace (treatment furnace) of a vertical low pressure CVD device used for selective epitaxial growth of Si or SiGe is formed of a reaction piping, an inlet flange, a seal cap, and the like, wherein a boat is placed on the seal cap, a wafer is placed on the boat, and the reaction furnace is heated by a heater.
In the above-mentioned structure, a gas serving as a raw material for the Si or SiGe selective epitaxial growth is introduced from an upper part of the reaction furnace through a nozzle and discharged from a lower part. Accordingly, in a reaction atmosphere where the wafer is present, the gas flows from the top to the bottom.
In this case, the heater heating the reaction furnace is divided into five regions of an upper heater, a central upper heater, a central heater, a central lower heater, and a lower heater, and a temperature gradient (temperature inclination) is set for the five divisional heaters in such a manner that the lower the region the higher is the temperature. A reduction in growth speed at the discharge side (the lower part of the reaction furnace), which is caused by consumption of the reaction gas, is corrected by the temperature gradient.
In the Si or SiGe selective epitaxial growth, a method of alternately supplying a raw material gas and an etching gas is employed. In the case of the method of alternately supplying a raw material gas and an etching gas, since the raw material gas supply and the etching gas supply are performed under an identical temperature, only one of a growth speed and an etching speed is adjusted by the temperature gradient of the heaters. That is, in the case where the temperature gradient is so set as to adjust the growth speed, the etching speed is decided in accordance with the temperature gradient. In the case where the temperature gradient is so set as to adjust the etching speed, the growth speed is decided in accordance with the temperature gradient.
Also, when the raw material gas and the etching gas are supplied from an identical nozzle, a film that is formed due to self-decomposition of the raw material gas deposits inside the nozzle, and particle generation and etching gas consumption are undesirably caused when the etching gas is fed through such nozzle.